Messages in this thread | | | From | Song Shuai <> | Date | Wed, 18 Jan 2023 02:37:09 +0000 | Subject | Re: [PATCH -next V7 6/7] samples: ftrace: Add riscv support for SAMPLE_FTRACE_DIRECT[_MULTI] |
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Evgenii Shatokhin <e.shatokhin@yadro.com> 于2023年1月17日周二 16:22写道: > > On 17.01.2023 16:16, Evgenii Shatokhin wrote: > > Hi, Song, > > > > On 17.01.2023 12:32, Song Shuai wrote: > >> > >> Hi, Evgenii: > >> > >> Evgenii Shatokhin <e.shatokhin@yadro.com> 于2023年1月16日周一 14:30写道: > >> > >>> > >>> Hi, > >>> > >>> On 12.01.2023 12:06, guoren@kernel.org wrote: > >>>> From: Song Shuai <suagrfillet@gmail.com> > >>>> > >>>> select HAVE_SAMPLE_FTRACE_DIRECT and HAVE_SAMPLE_FTRACE_DIRECT_MULTI > >>>> for ARCH_RV64I in arch/riscv/Kconfig. And add riscv asm code for > >>>> the ftrace-direct*.c files in samples/ftrace/. > >>>> > >>>> Signed-off-by: Song Shuai <suagrfillet@gmail.com> > >>>> Tested-by: Guo Ren <guoren@kernel.org> > >>>> Signed-off-by: Guo Ren <guoren@kernel.org> > >>>> --- > >>>> arch/riscv/Kconfig | 2 ++ > >>>> samples/ftrace/ftrace-direct-modify.c | 33 ++++++++++++++++++ > >>>> samples/ftrace/ftrace-direct-multi-modify.c | 37 > >>>> +++++++++++++++++++++ > >>>> samples/ftrace/ftrace-direct-multi.c | 22 ++++++++++++ > >>>> samples/ftrace/ftrace-direct-too.c | 26 +++++++++++++++ > >>>> samples/ftrace/ftrace-direct.c | 22 ++++++++++++ > >>>> 6 files changed, 142 insertions(+) > >>> > >>> The samples were built OK now, but ftrace-direct-multi and > >>> ftrace-direct-multi-modify report incorrect values of ip/pc it seems. > >>> > >>> I ran 'insmod ftrace-direct-multi.ko', waited a little and then checked > >>> the messages in the trace: > >>> > >>> # TASK-PID CPU# ||||| TIMESTAMP FUNCTION > >>> # | | | ||||| | | > >>> migration/1-19 [001] ..... 3858.532131: my_direct_func1: my > >>> direct func1 ip 0 > >>> migration/0-15 [000] d.s2. 3858.532136: my_direct_func1: my > >>> direct func1 ip ff60000001ba9600 > >>> migration/0-15 [000] d..2. 3858.532204: my_direct_func1: my > >>> direct func1 ip ff60000003334d00 > >>> migration/0-15 [000] ..... 3858.532232: my_direct_func1: my > >>> direct func1 ip 0 > >>> rcu_sched-14 [001] ..... 3858.532257: my_direct_func1: my > >>> direct func1 ip 0 > >>> insmod-415 [000] ..... 3858.532270: my_direct_func1: my > >>> direct func1 ip 7fffffffffffffff > >>> <idle>-0 [001] ..s1. 3858.539051: my_direct_func1: my > >>> direct func1 ip ff60000001ba9600 > >>> <idle>-0 [001] dns2. 3858.539124: my_direct_func1: my > >>> direct func1 ip ff60000001ba9600 > >>> rcu_sched-14 [001] ..... 3858.539208: my_direct_func1: my > >>> direct func1 ip 0 > >>> [...] > >>> > >>> If I understand it right, my_direct_func1() should print the address of > >>> some location in the code, probably - at the beginning of the traced > >>> functions. > >>> > >>> The printed values (0x0, 0x7fffffffffffffff, ...) are not valid code > >>> addresses. > >>> > >> The invalid code address is only printed by accessing the schedule() > >> function's first argument whose address stores in a0 register. > >> While schedule() actually has no parameter declared, so my_direct_func > >> just prints the a0 in the context of the schedule()'s caller and > >> the address maybe varies depending on the caller. > >> > >> I can't really understand why tracing the first argument of the > >> schedule() function, but it seems nonsense at this point. > > > > The question is, what should be passed as the argument(s) of > > my_direct_func() in this particular sample module. The kernel docs and > > commit logs seem to contain no info on that. > > > > With direct functions, I suppose, the trampoline can pass anything it > > wants to my_direct_func(), not just the arguments of the traced function. > > > > I'd check what these sample modules do on x86 and would try to match > > that behaviour on RISC-V. > > I have checked ftrace-direct-multi.ko and ftrace-direct-multi-modify.ko > on 6.2-rc4 built for x86-64 - yes, ip/pc in the traced function should > be passed to my_direct_func(). > > ftrace-direct-multi.ko: > # TASK-PID CPU# ||||| TIMESTAMP FUNCTION > # | | | ||||| | | > insmod-10829 [000] d.h1. 1719.518535: my_direct_func: ip > ffffffff87332f45 // wake_up_process+0x5 > rcu_tasks_kthre-11 [000] ..... 1719.518696: my_direct_func: ip > ffffffff8828d935 // schedule+0x5 > insmod-10829 [000] ..... 1719.518708: my_direct_func: ip > ffffffff8828d935 > systemd-journal-293 [001] ..... 1719.518823: my_direct_func: ip > ffffffff8828d935 > systemd-1 [000] ..... 1719.519141: my_direct_func: ip > ffffffff8828d935 > <idle>-0 [001] ..s1. 1719.521889: my_direct_func: ip > ffffffff87332f45 > <idle>-0 [000] d.s2. 1719.521901: my_direct_func: ip > ffffffff87332f45 > rcu_preempt-15 [001] ..... 1719.521917: my_direct_func: ip > ffffffff8828d935 > [...] > > The ip values are wake_up_process+0x5 and schedule+0x5, the locations > where the execution of the traced functions resumes after the Ftrace > trampoline has finished. > > The results with ftrace-direct-multi-modify.ko are similar to that. > > The samples look like a demonstration, that one can pass anything > necessary to the handler in case of "direct" functions. > > I suppose, the RISC-V-specific asm code in these two sample modules > could be updated to pass the saved pc value to my_direct_func() in a0.
Yes, you're right.
I added 'mv a0,t0' in front of `call my_direct_func` to pass the address of traced function with mcount offset.
Here is the updated patch for your reference. https://github.com/sugarfillet/linux/commit/95b174fb104dd970b982ee6fa19879393e229318
> > > > >> > >> As for this patch, it just impls a simple mcount (direct_caller) to > >> trace kernel functions, and basically saves the necessary ABI, > >> call the tracing function, and restores the ABI, just like other > >> arches do. > >> so It shouldn't be blamed. > >> > >> I started an independent patch to replace schedule with kick_process > >> to make these samples more reasonable. And It has no conflict with the > >> current patch, so we can go on. > >> > >> Link: > >> https://lore.kernel.org/linux-kernel/20230117091101.3669996-1-suagrfillet@gmail.com/T/#u > >> > >>> The same issue is with ftrace-direct-multi-modify.ko. > >>> > >>> Is anything missing here? > >>> > >>>> > >>>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > >>>> index 307a9f413edd..e944af44f681 100644 > >>>> --- a/arch/riscv/Kconfig > >>>> +++ b/arch/riscv/Kconfig > >>>> @@ -112,6 +112,8 @@ config RISCV > >>>> select HAVE_POSIX_CPU_TIMERS_TASK_WORK > >>>> select HAVE_REGS_AND_STACK_ACCESS_API > >>>> select HAVE_FUNCTION_ARG_ACCESS_API > >>>> + select HAVE_SAMPLE_FTRACE_DIRECT > >>>> + select HAVE_SAMPLE_FTRACE_DIRECT_MULTI > >>>> select HAVE_STACKPROTECTOR > >>>> select HAVE_SYSCALL_TRACEPOINTS > >>>> select HAVE_RSEQ > >>>> diff --git a/samples/ftrace/ftrace-direct-modify.c > >>>> b/samples/ftrace/ftrace-direct-modify.c > >>>> index de5a0f67f320..be7bf472c3c7 100644 > >>>> --- a/samples/ftrace/ftrace-direct-modify.c > >>>> +++ b/samples/ftrace/ftrace-direct-modify.c > >>>> @@ -23,6 +23,39 @@ extern void my_tramp2(void *); > >>>> > >>>> static unsigned long my_ip = (unsigned long)schedule; > >>>> > >>>> +#ifdef CONFIG_RISCV > >>>> + > >>>> +asm (" .pushsection .text, \"ax\", @progbits\n" > >>>> +" .type my_tramp1, @function\n" > >>>> +" .globl my_tramp1\n" > >>>> +" my_tramp1:\n" > >>>> +" addi sp,sp,-16\n" > >>>> +" sd t0,0(sp)\n" > >>>> +" sd ra,8(sp)\n" > >>>> +" call my_direct_func1\n" > >>>> +" ld t0,0(sp)\n" > >>>> +" ld ra,8(sp)\n" > >>>> +" addi sp,sp,16\n" > >>>> +" jr t0\n" > >>>> +" .size my_tramp1, .-my_tramp1\n" > >>>> + > >>>> +" .type my_tramp2, @function\n" > >>>> +" .globl my_tramp2\n" > >>>> +" my_tramp2:\n" > >>>> +" addi sp,sp,-16\n" > >>>> +" sd t0,0(sp)\n" > >>>> +" sd ra,8(sp)\n" > >>>> +" call my_direct_func2\n" > >>>> +" ld t0,0(sp)\n" > >>>> +" ld ra,8(sp)\n" > >>>> +" addi sp,sp,16\n" > >>>> +" jr t0\n" > >>>> +" .size my_tramp2, .-my_tramp2\n" > >>>> +" .popsection\n" > >>>> +); > >>>> + > >>>> +#endif /* CONFIG_RISCV */ > >>>> + > >>>> #ifdef CONFIG_X86_64 > >>>> > >>>> #include <asm/ibt.h> > >>>> diff --git a/samples/ftrace/ftrace-direct-multi-modify.c > >>>> b/samples/ftrace/ftrace-direct-multi-modify.c > >>>> index d52370cad0b6..10884bf418f7 100644 > >>>> --- a/samples/ftrace/ftrace-direct-multi-modify.c > >>>> +++ b/samples/ftrace/ftrace-direct-multi-modify.c > >>>> @@ -21,6 +21,43 @@ void my_direct_func2(unsigned long ip) > >>>> extern void my_tramp1(void *); > >>>> extern void my_tramp2(void *); > >>>> > >>>> +#ifdef CONFIG_RISCV > >>>> + > >>>> +asm (" .pushsection .text, \"ax\", @progbits\n" > >>>> +" .type my_tramp1, @function\n" > >>>> +" .globl my_tramp1\n" > >>>> +" my_tramp1:\n" > >>>> +" addi sp,sp,-24\n" > >>>> +" sd a0,0(sp)\n" > >>>> +" sd t0,8(sp)\n" > >>>> +" sd ra,16(sp)\n" > >>>> +" call my_direct_func1\n" > >>>> +" ld a0,0(sp)\n" > >>>> +" ld t0,8(sp)\n" > >>>> +" ld ra,16(sp)\n" > >>>> +" addi sp,sp,24\n" > >>>> +" jr t0\n" > >>>> +" .size my_tramp1, .-my_tramp1\n" > >>>> + > >>>> +" .type my_tramp2, @function\n" > >>>> +" .globl my_tramp2\n" > >>>> +" my_tramp2:\n" > >>>> +" addi sp,sp,-24\n" > >>>> +" sd a0,0(sp)\n" > >>>> +" sd t0,8(sp)\n" > >>>> +" sd ra,16(sp)\n" > >>>> +" call my_direct_func2\n" > >>>> +" ld a0,0(sp)\n" > >>>> +" ld t0,8(sp)\n" > >>>> +" ld ra,16(sp)\n" > >>>> +" addi sp,sp,24\n" > >>>> +" jr t0\n" > >>>> +" .size my_tramp2, .-my_tramp2\n" > >>>> +" .popsection\n" > >>>> +); > >>>> + > >>>> +#endif /* CONFIG_RISCV */ > >>>> + > >>>> #ifdef CONFIG_X86_64 > >>>> > >>>> #include <asm/ibt.h> > >>>> diff --git a/samples/ftrace/ftrace-direct-multi.c > >>>> b/samples/ftrace/ftrace-direct-multi.c > >>>> index ec1088922517..a35bf43bf6d7 100644 > >>>> --- a/samples/ftrace/ftrace-direct-multi.c > >>>> +++ b/samples/ftrace/ftrace-direct-multi.c > >>>> @@ -16,6 +16,28 @@ void my_direct_func(unsigned long ip) > >>>> > >>>> extern void my_tramp(void *); > >>>> > >>>> +#ifdef CONFIG_RISCV > >>>> + > >>>> +asm (" .pushsection .text, \"ax\", @progbits\n" > >>>> +" .type my_tramp, @function\n" > >>>> +" .globl my_tramp\n" > >>>> +" my_tramp:\n" > >>>> +" addi sp,sp,-24\n" > >>>> +" sd a0,0(sp)\n" > >>>> +" sd t0,8(sp)\n" > >>>> +" sd ra,16(sp)\n" > >>>> +" call my_direct_func\n" > >>>> +" ld a0,0(sp)\n" > >>>> +" ld t0,8(sp)\n" > >>>> +" ld ra,16(sp)\n" > >>>> +" addi sp,sp,24\n" > >>>> +" jr t0\n" > >>>> +" .size my_tramp, .-my_tramp\n" > >>>> +" .popsection\n" > >>>> +); > >>>> + > >>>> +#endif /* CONFIG_RISCV */ > >>>> + > >>>> #ifdef CONFIG_X86_64 > >>>> > >>>> #include <asm/ibt.h> > >>>> diff --git a/samples/ftrace/ftrace-direct-too.c > >>>> b/samples/ftrace/ftrace-direct-too.c > >>>> index e13fb59a2b47..3b62e33c2e6d 100644 > >>>> --- a/samples/ftrace/ftrace-direct-too.c > >>>> +++ b/samples/ftrace/ftrace-direct-too.c > >>>> @@ -18,6 +18,32 @@ void my_direct_func(struct vm_area_struct *vma, > >>>> > >>>> extern void my_tramp(void *); > >>>> > >>>> +#ifdef CONFIG_RISCV > >>>> + > >>>> +asm (" .pushsection .text, \"ax\", @progbits\n" > >>>> +" .type my_tramp, @function\n" > >>>> +" .globl my_tramp\n" > >>>> +" my_tramp:\n" > >>>> +" addi sp,sp,-40\n" > >>>> +" sd a0,0(sp)\n" > >>>> +" sd a1,8(sp)\n" > >>>> +" sd a2,16(sp)\n" > >>>> +" sd t0,24(sp)\n" > >>>> +" sd ra,32(sp)\n" > >>>> +" call my_direct_func\n" > >>>> +" ld a0,0(sp)\n" > >>>> +" ld a1,8(sp)\n" > >>>> +" ld a2,16(sp)\n" > >>>> +" ld t0,24(sp)\n" > >>>> +" ld ra,32(sp)\n" > >>>> +" addi sp,sp,40\n" > >>>> +" jr t0\n" > >>>> +" .size my_tramp, .-my_tramp\n" > >>>> +" .popsection\n" > >>>> +); > >>>> + > >>>> +#endif /* CONFIG_RISCV */ > >>>> + > >>>> #ifdef CONFIG_X86_64 > >>>> > >>>> #include <asm/ibt.h> > >>>> diff --git a/samples/ftrace/ftrace-direct.c > >>>> b/samples/ftrace/ftrace-direct.c > >>>> index 1f769d0db20f..2cfe5a7d2d70 100644 > >>>> --- a/samples/ftrace/ftrace-direct.c > >>>> +++ b/samples/ftrace/ftrace-direct.c > >>>> @@ -15,6 +15,28 @@ void my_direct_func(struct task_struct *p) > >>>> > >>>> extern void my_tramp(void *); > >>>> > >>>> +#ifdef CONFIG_RISCV > >>>> + > >>>> +asm (" .pushsection .text, \"ax\", @progbits\n" > >>>> +" .type my_tramp, @function\n" > >>>> +" .globl my_tramp\n" > >>>> +" my_tramp:\n" > >>>> +" addi sp,sp,-24\n" > >>>> +" sd a0,0(sp)\n" > >>>> +" sd t0,8(sp)\n" > >>>> +" sd ra,16(sp)\n" > >>>> +" call my_direct_func\n" > >>>> +" ld a0,0(sp)\n" > >>>> +" ld t0,8(sp)\n" > >>>> +" ld ra,16(sp)\n" > >>>> +" addi sp,sp,24\n" > >>>> +" jr t0\n" > >>>> +" .size my_tramp, .-my_tramp\n" > >>>> +" .popsection\n" > >>>> +); > >>>> + > >>>> +#endif /* CONFIG_RISCV */ > >>>> + > >>>> #ifdef CONFIG_X86_64 > >>>> > >>>> #include <asm/ibt.h> > >>>> -- > >>>> 2.36.1 > >> > >> -- > >> Thanks, > >> Song > >> > > > > Regards, > > Evgenii > >
-- Thanks, Song
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